Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON):

Solution:
H,W = map(int, raw_input().split())
S = [raw_input() for _ in range(H)]
#solve by dycstra
#pad by max value
D = [[H*W]*W for _ in range(H)]
D[0][0] = 0
Q = [(0,0)]
while len(Q) > 0:
	cx,cy = Q.pop(0)
	for dx,dy in [(-1,0),(1,0),(0,-1),(0,1)]:
		x = cx + dx
		y = cy + dy
		if 0 <= x < W and 0 <= y < H and S[y][x] == "." and D[cy][cx] + 1 < D[y][x]: 
			D[y][x] = D[cy][cx] + 1
			Q.append((x, y))

if D[H-1][W-1] < H*W:
	print sum([s.count(".") for s in S]) - D[H-1][W-1] - 1
else:
	print -1